Links and Resources

7. OGC Catalog services (CSW)

OGC® Catalogue Service for Web (CSW)- supports the ability to publish and search collections of metadata for data, services, and related information objects. Metadata in catalogues represent resource characteristics that can be queried and presented for evaluation and further processing by both humans and software. 

OGC Catalogue interface standards specify the interfaces, bindings, and a framework for defining application profiles required to publish and access digital catalogues of metadata for geospatial data, services, and related resource information.

There are two types of CSW: 


• Transactional CSW allows users to publish, edit and delete metadata; 
• 
Read Only CSW supports only metadata search and retrieval.


CSW enables metadata query using metadata core (mandatory) elements.

Searching in distributed catalogs

The process of searching in distributed catalogs involves the following steps: users formulate as accurately as possible their data queries. User ‘s request is posted to a Catalog Gateway (interface) responsible for registering the metadata content of different catalog services. This interface has to implement the ‘harvest’ operation in order to gather the metadata records stored in different distributed catalogs.  Thus, search request is transmitted to all registered catalog services. Each catalog service manages metadata entries and returns discovered metadata items to the users. 

Figure. Distributed search with common information model (Source: OGC Catalog services (CSW)- general model)

Thus an OGC CSW client should be able to query any OGC CSW catalogue, regardless of the underlying information model, using the elements defined in the common record schema and understand the response. With this model it is possible for an OGC CSW Client to query an OGC CSW AP ISO Catalogue.